The primary disadvantage of the fan construction in U.S. Pat. No. 3,219,143 consists, on the one side, in the difficulty presented when servicing the suction channel and the sound reducing plates. Both of these parts must be cleaned at regular time intervals, or the sound reducing plates must be replaced. To carry out such servicing, the blower which is fixedly mounted on the sound reducing plates must be removed. A further disadvantage is in the fans relatively large overall height, which is caused particularly by the sound reducing plates positioned on the suction side. For a sufficient operation of the sound reducing plates, same must be at least approximately 600 mm. long. A ventilating device of usual construction may then easily reach a height of 2 m. In the known roof fan according to U.S. Pat. No. 3,219,143, an impeller is used which stands vertically about its axis, however, the drive motor is above the impeller and thus enlarges the overall height. The motor must be arranged in this location to permit an easier servicing of the fan, because in this arrangement motor and blower are accessible from above by lifting off the fan enclosing cover for the fan.
U.S. Pat. No. 3,219,143 discloses a fan having an impeller with backwardly curved vanes. These impellers have in particular the disadvantage of a high noise development, which is contrary to the desired goal of sound abatement pursued by the use of a sound absorber. Therefore, fans are already known, the blowers of which have forwardly curved vanes. However, these blowers are always used as double-sized sucking blowers with a horizontal shaft. Therefore, these known constructions have the disadvantage of a very large overall height. In order to reduce the overall height of such a roof fan, it is known to construct the fan angularly. The thus achieved reduced overall height is, however, achieved through a much longer apparatus, particularly if also sound absorbers are used on the outlet side.
It is already known from German Gebrauchsmuster No. 1,901,791 to swingably secure a hood of a roof fan by means of a hinge, said hood being made of sheet metal. In this manner it is possible to easily provide access to the motor and blower during servicing. The access to the suction channels and the sound absorber is, however, not made easier in this manner because a removal of the entire blower is required.
The basic purpose of the present invention is to develop a roof fan of the above-mentioned type, in which suction tubes and sound reducing plates are easily accessible for the purpose of servicing and which is constructed in a compact and low design. Furthermore, the noise development of the fan is less than in known fans with forwardly curved vanes.
To attain this purpose, a roof fan of the above-mentioned type is utilized, which has the characteristics mentioned in the characterizing part of the main claim and additionally the characteristics mentioned in the subclaims.
The tilting mechanism of the housing surrounding the blower can be mounted on the casing of the air-quieting casing or the sound reducing device. The air-quieting casing forms a quieting zone for the conveyed air and increases the efficiency of the blower. The invention permits a lifting of the entire blower including the surrounding housing in a simple manner through a swivel movement off from the air-quieting casing or sound reducing device positioned thereunder. Same is then freely accessible from above and the sound reducing plates can be lifted out upwardly individually or together, which causes the suction channel to lie open for the servicing operation. Due to the inventive tiltable arrangement of the entire blower structure, it is possible, when a motor which does not lie within the impeller is used, to arrange said motor on the bottom side of the impeller without making the accessibility of the motor more difficult. By operating the inventively provided tilting mechanism, the motor, which from above is covered by the impeller, is easily accessible. Since this motor can project into the air-quieting casing or the upper free space of the sound reducing mechanism without effecting the air circulation, a reduction of the type of construction is achieved through the inventively arranged tilting mechanism also with respect to such known fans, in which the shaft of the impeller is arranged vertically.
The housing which surrounds the blower had regularly a greater diameter than the surface of the air-quieting casing or of the sound reducing device. Through the inventive arrangement of sound reducing devices (sound absorbers) on the pressure side of the blower in such a roof fan, neither the overall height nor the dimensions in the vertical projection of the roof fan are enlarged. Due to the fact that these sound absorbers on the pressure side are arranged removably or swingably at least on the tilting axis side, they do not make more difficult the hinging down of the blower from the casing or sound reducer positioned therebelow.
By using a blower which sucks air in on only one side and having an impeller with a large diameter and forwardly curved vanes and a spiral housing surrounding the impeller, the overall height is at the same time kept low and the same small sound development is achieved as in the known roof fans with forwardly curved vanes in which the fan is sucking on both sides and the impeller shaft extends horizontally.
For servicing the fan itself, it is advantageous to construct the lid of the housing surrounding the blower also in a conventional tiltable manner. This permits an easy access to the electric connecting means, for example, the controller, main switch and time switch, arranged in the fan housing. According to the invention, said lid of the blower housing is arranged tiltably about the same axis as the support plate itself, which carries the entire blower. In this construction, the lid is constructed preferably as a hood which overlaps the blower.
The lid, the sidewalls of the fan housing, and the surface of the sound absorbing hood are advantageously lined in a conventional manner with a not burnable, heat-insulating and sound-absorbing material. This achieves a reduction in the amount of condensed water accumulated to a minimum. Furthermore, it is advisable to provide a throttle valve for adjusting the size of the suction opening in the suction line either before or after the sound absorber on the suction side. If, in certain cases of use, the mounting of filters into the air path is necessary, then it is advisable to provide these in the air-quieting space before or behind the sound absorber, where they are easily accessible for cleaning due to the tiltable securement of the blower.
The blow-out openings can be covered on one or several sides by flaps to exclude undesired flow directions of the exiting air stream, for example, to avoid odors.